Melting of duplex steels are always challenging because of these steels are more affinity to gaseous concentrations such as hydrogen (H) and nitrogen (N) specially at high temperature and these gaseous will form blow holes in the components after solidification and its difficult to repair.
The question is how to keep these gaseous elements at lower level and what is the good melting practice for it.
atmospheric control and if you can use vacuum technology.
keep components free from moisture
I agree with Stuart but a vacuum furnace is not always available. The raw materials free of moisture is mandatory in any situation. You may install an Argon ring with a lid. My experience with this device was very effective in avoiding H and N pick up.
Thank you Stuart and Flavio for quick answer ,
This is common problem specially in coastline or a seashore foundry furnaces.
During the production of Duplex Stainless steel, Hydrogen and Nitrogen will be absorbed in some temperature condition only Which is not remember now. If you know that temperature, you can control that environment alone which will be reduce the H & N content. But Fully removing is not possible from my Experience
From our experience with melting duplex steels for semi laboratory semi production process we use quite clean and selected input materials. For melting was used the induction furnace without any atmosphere. But for industrial use the best way is to have a VOD or AOD at least (good should be VAD). But still for content of Cr more than 20% and low C it is difficult to not lose the Cr amount, so you have to degrees the pressure over the bath. As for problem with gases nitrogen is not a problem up to 0,04% from my experience do not generate porous.
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